- You’ll get this quest once you’ve completed Show No Mercy and report back to Elder Maxson aboard the Prydwen. Once you do, head down to the bridge of the Prydwen and Kells will pull you over and give you the assignment. Seems someone has been nicking food from the Brotherhood.

- To start the quest in earnest you need to speak to Knight Sergeant Gavil. Head down to Boston Airport (leap off the Prydwen in Power Armor, you know you wanna) and check the Airport’s main storage space, in the southeast of the area. Gavil should be standing near one of the entrances, and he’ll usher you away for a chat. Speak to Gavil on where to start and he’ll mention Knight Lucia and Initiate Clarke.

- Clarke should be standing in or near a cage with three generators nearby. (Look for a Fusion Core in the middle generator while you’re here.) Press him until he mentions Lucia, then, if you’re charismatic enough, you can press him a bit further for some bonus experience. Lucia should be nearer to the entrance. You can similarly press her about Clarke.

Knight Sergeant Gavil. He's kind of an ass.

- Return to Gavil and he’ll tell you to go looking for evidence of the crime. This will trigger a waypoint up on the Prydwen. Head to the Main Deck, then to the upper level, where the Brotherhood sleeps. There are footlockers here belonging to Lucia and Clarke. There are three Fusion Cores in Lucia’s footlocker, along with Knight Lucia’s Log, but it’s behind an Expert lock. Clarke’s contains From Lucia and Lucia’s Personal Key, which you can use to get into her footlocker if you couldn’t pick it yourself. (If you’re really bad at this, Clarke’s Personal Key is under his pillow. Eesh.)

- Read Knight Lucia’s Log, then head back to Boston Airport. Lucia should be standing more or less where you left here. Talk to her about what you’ve found and she’ll ask you to shadow Gavil. Do so after he finished work and he’ll lead you on a little chase around the outside of the Airport and into the Boston Airport Ruins. So long as you keep your distance he’ll eventually make his way here. (Sneaking is not hard. Trust me. I had Danse tromping around near me and Clarke didn’t seem to notice.)

Boston Airport Ruins. Bet you didn't think Feral Ghouls
would show up during this quest.

Boston Airport Ruins

- Now you need to find Clarke. Proceed until you see elevators. The one working elevator is jammed, so take a right and look for double doors. You’ll be forced down one level, where Ghouls will begin to appear. They’re of the obvious and sneaky variety, so be ready for a fight at all times. Once you’ve cleared the Ghouls, look on the left side of the not-so-moving walkways for a small side hall with a BoS corpse. Check it for Knight Rylan’s Holotag.

- When you take a left ahead you’ll find a partially-flooded section with more Ghouls to kill. They emerge from nowhere, but they’re also kinda slow about it, so you have plenty of warning. An explosive should slag ‘em easy. The hallway ends, but there’s a ramp up a level on your right.

- Follow the next hallway until you reach a parking garage. More Ghouls are waiting to hit you here, though they come in waves, so they’re not too bad. Take a left here and you’ll find the tunnel clogged, but there’s an Advanced locked safe on your left, sitting in the rubble. Pop it open if you feel like goodies. Take a right and you’ll find more Ghouls as you progress. No big deal, but be veeeery careful about hitting the cars if you use explosives (or even just guns). They blow up good.

- The path continues winding downward, with more Ghouls to kill. There are two elevators ahead of the entrance which you can use to drop to the lowest level, if you prefer stealth, to avoid a few fights. Near the bottom of the parking structure you’ll come across a small crowd of Ghouls, including a potent Glowing One. Exploding cars can make this fight really easy if you lure the thing properly. If you go all the way to the end you’ll find the rest of the structure flooded; check the back of one of the trucks for some ammo.

- There are turnstiles here that will take you onto a subway platform. (Look on your left if you get lost and wind up at the water, forcing you to turn back.) There are plenty more Ghouls here. Kill them as you like, but you can easily mine them to death at the entrance to the subway, as it’s niiiice and narrow. There are small rooms on your left and right, but they don’t contain anything terribly interesting.

- Hop into the water and head southwest on track level. You can either enter the train on your left or stay outside, though entering is wiser, as there are plenty of useful items inside - and you’re given an excellent shooting gallery angle of the Ghouls on the next platform ahead. Get on the platform and you can find a side room on your left. Along with some more items is a Novice terminal; hacking this terminal will allow you to switch on two Turrets watching the platform. (If you’re feeling stealthier, you can slip into this room from the train, turn on the Turrets, and watch them wipe out the Ghouls for you… though you’ll also have to deal with the Turrets.)

- The luggage area is up next. Guess what? More Ghouls! Aside from the would-be-zombies in residence and an assortment of items in the bathrooms and the luggage, the main item of interest here is the terminal between the two sets of stairs. It seems innocuous, but if you check its entries you’ll receive locations for the Beantown Brewery, the Shamrock Taphouse, Fallon’s Department Store, Haymarket Mall, Jamaica Plain, and the Boston Public Library. There’s also an entry for the Freedom Trail, which is part of a major storyline quest.

Initiate Clarke. Also, my shoulder.

- Take the down stairs. You’ll find Clarke down here, and he’s been… doing… things. Needless to say, he’s guilty. There are a number of ways to play this out:

Decide to kill the Ghouls. This will turn Clarke hostile, whether you express your intentions in conversation or just start blasting. He’s not difficult to kill. (Though Danse will hate if you have to kill him. Consider ditching the paladin if you brought him along.) You’ll also get this result if you decide to condemn Clarke. You can potentially get Clarke to stand down, but it takes a lot of convincing. You can then grab the Airport Employee ID Card off of the desk and use it to enter the room with the Ghouls. Initiate Clarke’s Log, on his body, also shines more light on what he was doing.

Tell Clarke to turn himself in. This requires a bit of convincing. You can do it more easily if you collected Knight Rylan’s Holotag earlier.

Promise to lie for Clarke. This will settle things for him, more or less.

Tell him to run. More or less the same results as lying.

Your choice made, use the nearby elevator to return to the surface, then head to the Prydwen and speak to Kells on the bridge. He’ll ask for results. Again, multiple things can happen:

Say that Clarke is responsible. If you convinced Clarke to turn himself in Kells will give you 200 Bottlecaps for uncovering the truth.

Say that Clarke is responsible. If you told Clarke to flee you’ll only get 100 Bottlecaps. You’ll also get 100 Bottlecaps if you killed Clarke and say as much.

Lie to Kells. If you’re persuasive you can convince him that Ghouls stole the supplies, and earn 50 Bottlecaps for your work. Any other lie will earn you nothing.

Regardless of what you tell Kells, the quest ends at this point. You’ll then gain the quest Leading by Example.

Whether you killed Clarke or spared him, you can use the ID Card he gives you to pop down and kill all of the Ghouls. There are a lot of them, so be careful. Don’t draw them too quickly, as there’s one particularly nasty Irradiated Glowing One in a side room that’s basically a boss-level threat. Don’t engage it unless you’ve cleared out everything else, and consider activating the Protectron near the stairs before bringing it out to play. You need to take the Glowing One down to clear the optional objective of killing all of the Ghouls, assuming you killed Clarke. Other than an Advanced locked safe and a Fusion Core, though, you aren’t missing a ton down here, so killing him isn’t the greatest option.